a) To solve this proportion, we can cross-multiply:

x * 4 = 8 * 5

4x = 40

Dividing both sides by 4, we get:

x = 10

Therefore, the value of x is 10.

b) To solve this proportion, we can cross-multiply:

3x * (2 1/4) = 2.7 * (1/3)

To simplify the right side, we can convert 2 1/4 to an improper fraction:

2 1/4 = 9/4

Now we have:

3x * (9/4) = 2.7 * (1/3)

Multiplying both sides by 4/9 to isolate x, we get:

3x = 2.7 * (1/3) * (4/9)

Simplifying the right side, we have:

3x = 0.3 * (4/9)

3x = 0.13333333333333333

Dividing both sides by 3, we get:

x = 0.13333333333333333 / 3

x ≈ 0.04444444444444444

Therefore, the value of x is approximately 0.04444444444444444.

c) To solve this proportion, we can cross-multiply:

2x * 0.6 = 16 * 0.3

1.2x = 4.8

Dividing both sides by 1.2, we get:

x = 4.8 / 1.2

x = 4

Therefore, the value of x is 4.